One of the biggest gaming sensations is hitting a sweet spot with millions of americans. Many moms included. It's called candy crush, and it's giving many gamers the same kind of rush as real candy. Tonight, though, some are warning that people are getting too hooked, with many families paying the price. Here's abc's reena ninan. Reporter: They are the bright, shiny, sugary candies that many are finding hard to put down. Some even choosing to game over the family. Well, I was on vacation in cancun and I'd find myself leaving the pool to go back to the room and I'd be playing candy crush, trying to get to the next level. Reporter: Like 53-year-old denise, 100 million people worldwide play candy crush every day. The game is pretty simple. Swipe the candy pieces in any direction to match and crush three or more of the same pieces. After a certain level, you have to pay to continue. The maker of candy crush, king, pulls in as much as $636,000 each day. 231 million a year of players hungry to get to the next level. There are reasons why players just can't seem to put the game down. Look at the colors. I mean, they really are beautiful. Very soothing music. The voice that gives you the positive reinforcement. Sweet! Reporter: And like playing vegas slots, there are rewards to keep you going. This whole idea of, you're achieving, it feels good, after awhile, you just keep playing to get that dopamine released. Reporter: Sorry, doctor, what did you say? See what I mean? Reporter: Smart devices are loaded with games from angry birds to words with friends and farmville. Designed to lure you in to keep playing. Some even include what's called a visual sparkle every six seconds to keep you engaged. Unlike some other gaming apps that hire trained sigh come jilss to be consultants to make their games more rewarding, king tells abc news, the company, quote, does not employ sigh come jilss or behavioral economists to provide input on its games. King, the maker of candy crush, tells us 70% of its players in the u.S. Are woman. I spotted a woman playing it on the subway today. She said she's been on level 23 for the past week, debt pratt to move on. Stuck on 23. One of the crew members said he had to take it off his iphone because he couldn't stop playing.

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